Chesapeake Times, Vol 11 | Oct 2022
In SonarWiz 7.10.00, we are introducing a new geodetic engine. The new engine is based on the popular open-source PROJ library and gives SonarWiz support for modern dynamic datums, datum ensembles and derived projected coordinate reference systems (CRS) we have not been able to support in previous versions of SonarWiz.
Why did we decide to switch geodetic libraries?
The geodetic library is responsible for accurately converting a geographic position on the Earth (latitude, longitude and altitude) into, and out of, the Cartesian coordinate system (X,Y,Z) used internally by SonarWiz. In other words, it isolates our Sonar processing code from the code necessary to plot the data accurately on the Earth. Our old geodetic library has been under active development since the early days of SonarWiz (late 1990s). We had several reasons for making the change now:
First, over the past decade, we have found it increasingly difficult to support the advanced transformation pipelines required by modern national surveys using our existing code. National mapping agencies frequently update their geodetic frameworks to increase the accuracy of positioning systems over their territories. These updates account for plate movement of the continents; isostatic (vertical) changes due to groundwater removal, sea level rise and residual ice-age effects; and adjustments resulting from modernization of national survey networks. Sometimes, new transformation algorithms are developed to achieve improved accuracy. And many modern datums have an Epoch or time component that accounts for regular motion of the framework over time. Our older library was not developed with the necessary flexibility required to support all of these updates. The PROJ library we based our new geodetic engine on supports all of these necessary operations.
Second, we wanted a library that was more standards compliant. Back in the early 2000’s, there were no clear standards for specifying geodetic metadata. Today, that space is greatly reduced to the IOGPs EPSG database which follows the ISO 19111:2019 international standard for referencing by coordinates, and the de facto standard created by ESRI’s dominant ArcGIS. The PROJ library is a reference implementation of the EPSG specification and also is compatible with ESRIs geodetic parameters. We expect that it will be easier to create SonarWiz projects using existing spatial references and easier to export data out of SonarWiz into your GIS or CAD software.
Third, we wanted a geodetic library that was widely used, well supported, and easy to update as needed. Keeping up with all of the changes required to support mapping agencies throughout the world is a herculean task for a small company like CTI. Sometimes the changes require specialized geodetic expertise that we do not have in-house. The PROJ library is used in dozens of widely-used open-source and commercial products. A number of national mapping agencies have directly contributed to the library to implement state-of-the-art processing pipelines. We feel confident that using a major open source library like this is better for our customers than trying to maintain our own system. It will allow CTI Engineers to focus on sonar processing, our core business
How will this impact my use of SonarWiz?
SonarWiz stores geodetic parameters in a database. The parameters are looked up by name using a spatial reference id (SRID) stored in the project MML file. The SRIDs of the new geodetic engine are different from the old engine. If you open a project in SonarWiz 7.10.00 and it doesn’t recognize the SRID of your existing project, you will see the following dialog asking you to pick a new the Project CRS:
The dialog will suggest a matching coordinate system, but take care to ensure that they are, in fact, a match.
If you try to open a project using the new SRIDs in an older version of SonarWiz, you will not get a friendly Geodesy Update warning – older versions of SonarWiz are not expecting this database change. Still, you need to do the same thing. Open up the Project Settings dialog and pick a matching coordinate system from the list.
Once this is done, the project will behave as usual.
For customers using custom coordinate systems in their projects, there is an additional step required to promote a project to SonarWiz 7.10.00 or to roll back from the new version to SonarWiz 7.09.04. You must first manually add the custom coordinate system to the target version of SonarWiz before you switch engines. Otherwise, you won’t have the custom option available to pick when the dialogs open. Unfortunately, the automatic update mechanism used to load custom coordinate systems into SonarWiz when they are detected in a project, does not work when you switch between geodetic engines.
For More information:
We have added a FAQ page about the new geodetic engine switch to our Help Desk where we will answer customer questions as they arise:
As always, please feel free to contact us if you have any additional questions.